Insert having internal drive grooves



J. ROSAN June 22, 1965 INSERT HAVING INTERNAL DRIVE GROOVES 4 Sheets-Sheet 1 Filed Dec. 4. 1961 I INVENTOR. Jose Rosan BY TTOR/VE Y June 22, 1965 J. RosAN INSERT HAVING INTERNAL DRIVE GROOVES 4 Sheets-Sheet 2' Filed Dec. 4. 1961 INVENTOR. 70 55 osalz V QTTORNEY June 22, 1965 J. RosAN 3,190,169

INSERT HAVING INTERNAL DRIVE GROOVES Filed Dec. 4. 1961 4 Sheets-Sheet 3 I NVENTOR.

JFI. /4. U3 Ike/K7807 flTToRNEY United StatesPatent O This application is a continuation in art ofapplication Serial No. 640,470, filed February 15, 1957, which, in turn, is a continuation-impart of application Serial No.

Patented June 22, 1965 root will seriously interfere withthe wall strength. .In any event, the depth of the groove means should always be less than the depth of the thread.

618,594, filed October 26, 1956, both of which are now abandoned.

This invention relates to'inserts adapted to be installed in an opening in a work piece and characterized by the incorporation of an externally threaded'wall and an internally threaded bore. i Y Driving such inserts into the work piece 'opening has constituted a major problem in" the successfulutilization thereof. Typical'expedients utilized in prior art constructions have included the incorporation of polygonal Obviously, the number of drive grooves utilized will depend upon many factors; the torque imposed during driving; whether the insert is self-tapping, and the like. Therefore, I do not desire the concept of my invention to be limited to the incorporation of any particular number of grooves. In addition, the arrangement of the drive grooves can be symmetrical-or assymmetrical. Among the many advantages accruing from an insert incorporating the teachings'of my invention is an extremely positive drive with the drive load extending the entire length of the insert. Moreover, the nature of the drive toolis such that the chordalarcs ofthethreads are efiectively cleared by the drive tool, resulting in unirne paired integrity of the thread.

Qt partic'ularirnportance is the fact that the drive groove means is so related to'the successive convolutions drive openingsat one extremity stare internally threaded bore, or the formation of polygonal drives through'th lengthof theinternal bore. e

I have found that it is possible to drive such inserts much more effectively by the provision of drive groove means in the wall of the internal bore. Thedrive groove means is formed in the bore wfll and intersects the successive convolutions of the internal thread todefine chordal arcs or arcuate thread segmentsin said internal thread.

Because of the provision of 'drive groove means of the character incorporated in inserts of the invention, it is possible to maintain the integrity of the internal thread of the insert, .thus providing-for adequate thread engage ment between the internal thread of the insert and a fastener disposed therein. Moreover, the drive groove means, being interposed between the chordal arcs of the internal thread, provides driving sides or faces which may be engaged by a toolhaving driving protuberances whose configuration conforms substantially to the configuration of the drive groove means, thus insuring that driving torque is equally distributed throughout the length of the insert.

Moreover, as will be described in greater detail below, the formation of the drive groove means with their bases or'bottoms disposed inwardly of the major diameter of the internal thread results in maintenance of the structural integrity of the internal thread with the consequent hoop strength achieved thereby. Thus, positive driving engagement with the drive groove means not attainable by prior art polygonal drives which do not offer the advantages bore.

of the internal thread as' to provide for a continuum through said suecessive convolutions. In other words, because the drive groove means are of less depth than the depth of the tread, the'root thereof is unimpaired and integral. Thus,- the hoop strength of the successive} convolutions of the internal thread is preserved, and the intermediate chordal arcs of the thread convolutions constituted by successive arcuate thread segments 'thus achieve a short'colurnnar etlect tending to resist .,dis

. placement or distortion when the drive tool is inserted in the groove meansto drive the insert into thework piece Therefore,' there is'no tendency for' the walls of the groove means to deflect away from the e'ngaging portions of the drive tool, and a uniform linear contact -is establishedalong the length of the drive toolg The linear uniformcontac't results ineven drive load 'distributionwith consequent elimination of points of stress concentration during the driving of the insert] means permits the application of substantially greater driving force without distortion of the cylindrical character of the insert as would occur in prior art polygonally formed devices. v

' The drive groove means of the invention can be provided in a variety of configurations and it is not intended that the teachings ofthe invention be limited to any particular configuration. For instance, I have utilized angularly configured grooves, rectangular grooves, semicircular grooves and the like. However, to preserve the integrity pf the 'internal thread,.it isessential that the Because of the, maintenance of thestru c'tural integrity of the successive convolutions ofthe internal thread and the consequent preservationof, the hoop strength of said successive convolutions, repeated removal and installation of'the insert from and into the bore in the work piece is feasible. This process is implemented by theshape of the drive groove means of the invention, which permits facile insertion and removal 'of the drivetool into the drive groove means of the internal bore of the insert. 1 Y, The depth 'of the driving groove means in either the four or six drive groove embodiment relative to the radius depth of the internal thread major diameter may vary from-25%to depending upon the. diameter of the internal thread, the type of thread, the type and/ or functional purpose of theinsert, that is, whether it is plain or self tapping, the, material in which the insert is to. be mounted, and the like. a v

It is essentialfora complete understanding of the teachings of the invention that the concept of the drive groove'means be visualized with'accuracy, Initially, as Will be described in greater detailbelow, the drive groove means are formed in the, cylindrical, wall of the internal bore, and subsequently, the internal thread is formed in saidlbore with the root of said thread disposedoutwardly of the bottom of the groove means. After the thread has been formed in the previously broached .Wall of the internal bore, each longitudinally oriented groove means is constituted by a successive seriesof aligned grooves formed in the successive convolutions of 'the internal thread. In essence, the individual grooves formedin the successive convolutions may be considered minor grooves which, together, constitute the major longitudinal drive groove of the invention. I

V I have found that the drive'groove means of the inven tion is particularly applicable to inserts characterized by 7 extremely thin walls;

In utilizing the teachings oi the invention in thin wall inserts, it'is of utmost importance; that the .drive'groove or. grooves be characterized by the elimination of sharp :angles at;- the bases thereof which would constitute stressv concentration'lines; Therefore;

even in" .triangularly broached," or otherwise formed groovesythe apex of-the triangle will be 'an included radius.'.''

Typical of the application of the teachings iofrny" inventionis the provision of: drive grooves in a' thin wall insert with the grooves arranged in a pattern which might be considered to be coincident-With the included angles of a square or hexagon. Of course, such a description is by way of analogy only since even when the grooves are 7 of angular configuration they are not poly'gonally included angles generated by planar surfaces.but,..rather,

gro'oves generated in the internalbore" while. still maintaining the structural integrity-of 'the thread in three ways; namely: I

. (l) By not permitting the groove depth to equal that V .of the thread; I I (2) By preserving mediate the drive groove or grooves;

- (3) By not permitting lines of stress concentration to the chordal arcs of the thread inter- 7 FIG. 22 is a diagrammatic view illustrating a driving. tool adapted for utilization in conjunction-withtheinbe created in the thread by theincorporation of sharp included angles in the bases 'ofthe grooves.

Other objects and advantages in-the' 'nvention willbe apparent from the following specification and theaccomtion onlyand'in which: I a 7 FIG; 1 is a top plan'vie'w of an insert constituting one panying drawings, ,whichare for the-purpose of illustra- 7 embodiment'of the'present invention with the groove means thereof-arrangedin afour. point-pattern; f

FIG. 2 is-a side sectional view of the insert'of FIG. 1;

FIG. 3 is aside viewof the insertot FIGS. :1 and 21 showing the fastener being driven into 'a'iWQl'k piecebore,

shown insection; bya drive tool adapted'to engage the groovemeansof the-insert; I

FIG. 15 is a bottornxplan view illustrating the engage- 3 ment of a 4-point drive tool withthe corresponding groove meansof the insert of FIGS. 1, 2, and 13 of the drawings; thetool being shown fragmentarily; V 1 FIG. .16. is a schematicview illustrating. the relationshop of the cutting edges of the broach andthe portions of said broach intermediategsaid cutting edges, respec tively, with the, internal; thread root .and'the contiguous chorda'l arcs" intermediate :the groove means; taken from the bottom as. shown by lirie16-16 of FIG. 14;

FIG. 1 7 is a diagrammatic view illustrating atypical driving tool for an insert of the characterfof FIGS; l

andl3;

FIG. 18 isa diagrammatic view illustrating atypical driving tool-for aninsert of the character. offFIG. 10;

. FIG. 19 is an enlarged fragmentary sectional view illus trati'ng particularlythe relationship between the" drive groove means and the corresponding-thread convolutions;

FIGL ZO. is a top plan .viewon'an enlarged scale: of the insert FIG.7 prior to theformationjof the threadslin' the 1" internal bore 'by"tapping; z

' FIGI21' is a diagrammaticview ofa drive tool adapted for utilization 'withthe insert of F IG. 7;" I v sert of FIG. 8;, a V

FIG." 23 is a fragmentary view toan enlarged scale,

1 showing additionaldetails of'theconstruction o'famodi fied formzof the drive groove of the insert.v

"Referring to the drawings; and .more particularly to FIGS; 11-3, 1' show an insert 10' which; may be ,of the FIG. 4 is a vertical 8601101131" view of another embodil ment of the invention installed in a work-piece;

FIG. 5 is a vertical sectional view of yet anotherliem-r bodiment of the invention;

FIG. 6 is a top plan view of another embodiment of the: invention showing the groove means thereof arranged in a modified octagonal Qpatter-n;

T FIG. 7 is a top plan view showmg another embbdirnent 0f the invention incorporating aasingle, rectangularly,

formedgroove means 7 g, FIG. 8 is'a. top plan view ofcyet another embodiment of the invention illustrating. theiutili'zation of twoangu i larly shaped groove'means;

, .FIGL9 is a vertical, partly sectional viewillustr ating: the formation-of the groove means in the Wall of them? ternal-boreof an insert havingsix driving grooves, before tapping;

' TFIG. 10 is averticaI sectional view on an enlarged scale of. aportion of the insert. of FIG. 9', taken'a's indi cated by line 10-10 in FIG. 11 after. tapping, illustrating f the formof the internal threadin the :previouslyLgrooved wall of thebor e; a

FIG. 11 is a bottom plan view showing the engage- V ment of the broachof FIG. 9 with the wall ofthe internal bore;

FIG.v 12 isf'an enlarged, fragmentary top plan view instant case; are four. in number.

A. setting tool 16 of substantially shown in FIGS. 1-3, the tool'16'wil1 interfit'a'nd-engage with the drive groove means: 15 of the insert 10 so that.

the insert may be rotatedin and, cut. threads in vthe bore- 18 of a work piece 19;.

v .Afterfthe insert rams been 'i'nstalledinthebore 18,lthef tool '16 can be readily withdrawn from operative engage? rnent' therewith. Facile installation and withdrawal 0f the drive tool into "and from operative engagement with the corresponding drive groove means ofthe inventionis one of the desirable characteristics of the invention w en; will bef'adverted to ingreater detail hereinb'elowQ er ;In the modification of the invention shownxin FIG; 4,

a fastener element ZGhas an externally threaded'porti'on '21 for insertion inthe' threaded bore 22 of, aworkpiece 23 and has a locatingjpin extension portion'24 adapted to extendinto' an aperture in a complementary work piece 25 to;be secured to work piece 23. --The locatingpin.

portion 24 is formed {with ajthread ed' bore 26, the

threads of which "are interrupted to form longit udinally extending grooves 27 adapted to be engaged'by a seating tool similar to toolylohaving a corresponding nurnber illustrating: the cohfigurationiof thelsuccessive convolu tions, ofthe, internal thread with the drive groove means formed therein;

FIG. 13 isja vertical partially sectional viewt onr an of the internal bore;

' 30 hasza slotted and tbeveledf'endfltla and self tapping threads 31 for seating in a bore 32. :of 'aworbpiec'e-e33 andhas a'threaded'borefi l formed with apln'r alit'ygine this case six, of longitudinal grooves. 35 similarto, grooves.

. 0 enlarged scale similar to the. embodiment 'of.FIG. 1 of the drawings; i V J FIG; 314 is .a vertical sectional yiew illustrating'the broaching of the longitudinal groove means in thewall.

" 15 and27 for thesarne seatingpurpose. v g V a The longitudinal grooves in the bore of the=fasteners may be of any-desired number or shape. 'Theffastener V of radial enlargements capable .of engaging grooyes' zT,

FIG. 4 shows a cap screw28 to be 'run in the bore 26; for securingworkpieceZS in contact with workpiece 23. 3

In. FIG; 5 iss'hown another modifiedforrn: of the in vention. In this figure arself-ta pping insert -or fastener squarecross section adapted for utilization in 5 conjunction with the insert 10 is mounted in a chuck 17 of a powertool and; 3S bSL 36 of FIG. 6 has internal threads 37 and longitudinal grooves 38 which are eight in number'and equally spaced circumferentially. The fastener, 40 of FIG. 7 has internal threads 41 and a single groove '42 which may be rectangular in shape and adapted to be engaged by the drive groove correspondingly threaded bore, not shown, in the work piece, and drive groove means 54have been-formed in the wall of the bore, 56 by a broach 60 incorporating a pilot 62 and a pluralityof-broaching points or lines'64 whose configuration corresponds to the desired ultimate configuration of the drive groove means 54.

The broachingoperationis illustrated in FIG the drawings and it willtbe noted, atlthis juncture, that the, drive groove means 54 formed in the wall 'of the bore 56 are angularly configured but are characterizedby the incorporation of radii at the base thereof. The incorporation of radii at the bases of the drive groove means 54 prevents the creation of lines of stress concentration, which, particularly in the case of thin wallinserts might result in failure thereof; these radii are designated :by the reference number 54A throughout.

After the formation of the drive groove means 54 in .the above-described manner, the wallof the bore 56 of the insert 50 is provided with an internal thread 70 which, as best shown in FIG. 10 of the drawings, is characterized by the fact that the major diameter of the thread root is disposed outwardly of the longitudinally extending groove means 54, as set forth dimensionally in tables appearing hereinbelow. In other words, the bottoms of the groove means 54 are disposed intermediate the major and minor diametersof the internal thread 70.

During the broachingprocess when the longitudinally oriented drive groove means 54 are formed in the abovedescribed manner, the portions 74 of the broach 60 intermediate the cutting points 64 leave the wall of the bore intermediate the drive groove means 54 undisturbed. Therefore, when the internal thread 70 is cutlin the 'wall of the internal bore 56, arcuate threaded segments constituting chordal arcs are formed in said wall to provide the successive convolntions'of the internal thread'7 0 with thread segments of unimpaired integrity.

. 6 the hoop. strength of the residual thread. The resist.- ance to such displacement correspondingly enhances'the columnarstrength of the longitudinally extending drive groove means 54. V,

Another aspect of the invention graphically illustrated in FIGS. 10 and 12 of the drawings is the radial'configuration of the bottoms or bases of the drive groove means 54. As a primary matter, it should be explained that the inserts 50 of the invention are found in a large range of sizes and that in the smaller .sizes, the radial configurationof 'the. bases orlbottoms of the groove means 54 mayjnot be readily perceptible to the naked eye; However, the radii are always present at the bases or bottoms of, the drive groove means'54" and prevent the, creation of linear stress 'concentrations which might result in the structural failure of the insert 50. Inconsidering'the' drive groove means 54, it willj-be'noted that after the internal thread 70 1138136611 formed in. the wall of the bore 56, the drive groove means5 4 are constituted by a series of verticallyaligned recesses 92 which, in essence, constitute minor groove means-which serve cooperatively to define the longitudinally extending major groove'means 54 of the invention. 1 u

The typical dimensions ofa thinwall insert 50 incorporating 6 drive groove means 54 are set forth hereinbelow in inches. The insert incorporates,a;# i -2Q, internal thread and a #Vz ZOexternal thread. i A=External major diameter, .500 B=External pitch diameter, ;.4675 I C=External minor diameter, .4620 'D- Internal minor diameter, .390 E=Internal pitch diameter, .409 F=Internal major diameter, .448

G=The single depth of the internal thread is .029;

H=,=The depthof the internal thread remaining between 0 12 of the-drawings Thus, when a drive tool 80, such as that shown in FIG. 18 of the drawings, is utilized in driving the insert 50 into a work piece, not shown, it will be provided with :successive engagementfpoints 82 arranged in a six drive groove pattern corresponding to the six drive groove pattern of the 'drive groovemeans 54 of the insert 50, and

the areas 84 of said drive tool intermediate said points will clear the chordal thread segments intermediate the drive groove means 54.

The relationship of the drive, groove means 54 wan ,the associated chordal thread segments is graphically illustrated in FIG. 12 of the drawings wherein the internal fthread is illustrated as incorporating a plurality of chordal segments whicli'are interposed between the drive groove means 54 and which are characterized by the presentation of unimpaired cooperating surfaces to the correspondingly formed male convolutions on a fastener inserted into the internal bore 56 of the insert 50. Also illustrated in FIGS. 10 and 12 of the drawings viding a-continuity of structural thread integritywhich resists axial and torsional displacement of the chordal qarc segmentsj90 of the internal thread 70 because of ;75

' groove means 118.

J=Angle of radiused .groove=approximately 120.included. i

" The percentage of the radial depth of the internal thread occupied by the drive groove means is 33.5% Another embodiment of the insert of the invention-is illustrated in FIG; 13 as constituted by acylin is provided with a plurality of the drive groove means .118.-

The drive groove means 118 ar e arranged ma four drive groove pattern. The drive groove means 118 are located intermediate chordal arc thread segments 119 whose terminal extremities are located adjacent the drive In fabricating the insert 110 the externalthread 114 is formed upon the external wall of the body 112; Subsequently, as shown in FIG. 14, a broach 130. having a pilot 132 and four successive syr'nmetricallyv arranged sets to the fabrication of the internal of successive cutting points or lines 134, 134, 134" is introduced into the bore 116. this manner,

the elongated, longitudinally extending .drive groove means 118 are formed in the wall of the bore 116 prior thread 120, and preferably parallel to the bore axis. r After the formation of the drive. groove means 118 in the above-described m anner, thein'ternal thread 120 'is formed in the bore by tapping said thread therein.

The thread root is disposed outwardly of the bases on bottoms of the drive groove means 118, as best shown in FIG. 13 of the drawings, said bases or bottoms being located intermediate the major and minor diameters of said thread and insuringstructurah'continuity of said .thread throughout all of the convolutions thereof.

The relationship of the broachwith the ultimately formed internal thread 120 isschematically illustrated in F IG. '16-o'f, the'drawings, wherein the cutting points 1340f said broach are illustrated'as'b eing disposed inter mediate the, major and minor diameters 140 and 142, re-

spectively,'of said thread. 'Moreover, the manner in which thepo'rtion's 144 of, the bro'ach130intermediate the cuttingpoints 134 clear-the contiguous areas of the Wallof the bore 116 intermediate the drive groove means 118 -isa1so illustrated inFIG. 16' or the drawings.

Atypical driving tool 150 "having'tour driving points 152 is illustrated iii FIG..17 of the drawings and shown engaged with the correspondingdrive groovemeans 118, 'in- FIG. 15 of the drawings. It will be notedthat as.

in the 'c as'eof the broach 130, the portions ofjthe driving ,tool;150'intermediate the. driving ,pointsf152' clear the chordal arc thr'eadseg'nients o'ffthe internal}, thread 12"0 .to preventdamage 'tothe thread segmentsdu'ring the driving operation.

a The dimensiehs or a .ty ich n 110 incorporating four .drive 'groove means are ;set..-forth hereinbelow in inches. The insert incorporates 'a' #6-321interhalthread and a #lo itlteiiternallthreadw I Y '.=External major diametei, $1970 1 Fi -External pitch diameter, I1 69 'C"=External minordiameter, L161 'D'=Inter'nal minorjdia'meter,1115*' E"= Internal"pitchdiameter, 21-19 'i F=Internalmajor diameter,-.'145

G'=The single depth ofjthejnterna'l thread'is 0l5.

siderably rigidifies the chordal arc thread segments 90,

which lie between adjacent drive 'groove'means 54',f and-- H '=The depth of internal thread remaining between the bases of the drive groove. means, 11$ and the major 'dimeter of said threadis10091. V

l,=Inter'na1 groove =radius, .0635 15015 the drawings). i

]=Angle of radiused' groove' approxiniately 12d". .in 'T I V eluded. V} The percentage (as indicated in offthe, radialfdepthiof the internal ,thre'ad :occupied bytherdrive groove'ineansisfGOZL V .The dimensional tables presenteafhereiuabove*consti-" tute a a basis for determining the amount '-of material left:

between the major diameter of the internal threadiand' Tthe ba'ses'of ithe'drive 'groove 'meajns'. 'It-should be unmearis is :always disposedinternallyof the-major diame- 'ter of the thread to provide the requisite thread strength 'I have found that anfeflfective rang'eof drive groove '7 means depth lies within a'rangefof 25 to 90% .of'the height of the internal thread where said height :is deter-- -mined by the dimension between the internalthre'ad major I and minordiameters; 'As stated. hereinabove, the =particular percentage of thread' height whichthe driv'egroove means consumesis avcrite'rion offthe specific type ofintern'al tbi'ead utilized. The percentagefof the radialdepth V of the internal threadc occupied bythewdrive" groove.

"means'is obtained by taking the difierencebetween-the 2 internal major diameter, Fraud twice the depth .of the -internal;g'roove-radius I, and dividing itby-thediiference betweenthe internal major: diameter F and the internal! "minor diameter D." J j I V 7.;

- ;For'example, in thecase of the 20-internal;and V 7 insert, described in' thetabula isgivienfa's L l-48', I as .ZI lQand D' as 390. r

divide F921 by F and multiplytby 100. 5

' dersto'odttliat in all casesthe?base..of thejdrive groove 7 means diet the insert 43.

' The relationship, between the various structural co m ponents {of the insert 50 jis ish own in greatly enlarged 1 fragmentary CI'OSSfSGCfiOIl inQFIG; 19 of. the drawings; Particularly illustratedinflfi 1'9 isthe manner, in which the major diameter portion of the' internal thread 701mm I stitutesan unbroken-continuum underlying the groove means 54 to achieve the requisite structural integrity, 0 thus. imparting the desired icolumnari effect to the drive v groove .meansi;54; @Perceptible :also' is the radiusflSflA V ."provided at the base of the, groove means 54 itopre-f- ,ventthe creation of stress concentration lines w h woul cause ultimate failure of the insert '50. 9

1 The consequenthoop strength of thejsuccessivei cone? volutions of-the internal thread resists deflection'of the longitudinally oriented drivegroovemeans 54,dur-

- ing the driving or removal of the-insert 50. Moreover,

the structural integrityof the internal thread 70 con ally and torsionally. a"

42 therein by. a b roaching operation similarto those described hereinabove; "Of-cohrse', t'he thread-41 is siibse- 7 quently formed in the bore of 'theinseit '40." ,A drive tool 1 7i) is shown inFIG. 121 as having 'a cylindrical body 1jf72 and a radial key'orprotuberance 174 adapted. to engage in the corresponding drive groove'rneans 42 A, drive tool ldi adapt ed to be futiliied in driving the.

insert of FIG. 8 into a work piece bore is illustrated" in FIGLZ Zof the drawings.- The drive tool 180'i'ncludes a cylindrical body 182 having radial ,protuberances 18,4 7 adapted to be inserted in'the corresponding drive groove It will be observed thatin the embodiments, such as ,that of'FIG. 8 andlthecorresponding tool of 'EI G 22',i

the more'acute the angle between the ends'of the adja-i 7 cent. chordal segments, the greater. the iresistanceto the. columnar loading imposed by engagement with a-tool having corresponding radial protuberance configurations;

*This avoids "distorting thecylindrical shape of them .sert when force is exerted :b'y'ja driving tool; The; same principle may be appliedto the driving groove 'of'the in-.

serts shown in the other figures.

An alternative embodiment 50'f of the insert "of the invention visdisclosed in enlarged. fragmentary jfo'rm in; FIG. 23.0mm drawings as'incorporating drive groove means; 54' oflslightlydifierent configuration fromKthe. drive groove means,:54 'of the. insert f50.-- The drive groove means 54' of theinsert 50' is. characterized by a the incorporation of a broaderbase'which, in turn, in-

corporates a plurality of radii 54A, the adjacent chordal 1 thread segmentbeing indicatedat t i V As'previo'nsly disclosed, the drive groove means of the invention may be'fo'rmed in any configuration including "semi-circular. Howevenwhere the drive groove'means 70 a e r of angularity of, the 'walls of the groove c-onstitutedby'the J entremitiespf the chord-a1 arcs is "determined by suchfaca tors 'asithe torque" necessary :to install-the insert; the ,pitch of the external is tormedfto incorporate an included. angle, the degree 7 threads the depth ofrthe' external threads and the like. However. itshould he noted that in order to provide for driving engagement with the driving tool, the Walls of the drive groove means must be disposed at such an angle as to transmit the driving force into the chordal arc segments of the internal thread in such a direction that the tendencly to distort the insert 'wall outwardly will be minimized. The direction in which the driving force is appliedshould be asnearly as possible tangent to the insert wall adjacent the point of application of the driving force. 7

Therefore, the various embodiments of the insert of the invention described hereinabove are characterized by certain salient and significant structural features which include the provision of longitudinally extending drive groove means inthe bore of the insert, said drive groove means having their bases locatedintermediate the major and minor diameters, of the internal thread of said bore; the preservation of the structural integrity of the internal thread by the retention of the major diameter portions of the root of the thread in underlying relationship with the drive groove means; the provision of drive groove rneans'of a variety of configurations asdetermined by an end view thereof; the. symmetrical disposition of the drive groove means in the wall of the bore or, conversely, the asymmetrical distribution thereof; and the provi- "sion of thread portions or chordal arc thread segments of unimpaired integrity which afford columnar strength during rotation of the insert for either insertion or removal, these columnar portions providing for strengthened engagement with a correspondingly threaded male element.

As a consequence of the incorporation of the saiiient features of construction set forth hereinabove, an insert having drive characteristics .unobtainable with prior art constructions is achieved. Repeated insertion and removal of the insert is feasible because of the elimination of distortion or deflection of the drive groove means by maintaining the structural integrity of the internal thread major. diameter portion.

Furthermore, repeated removal of the associated male fastener from the bore of the insert is feasible because of the fact that the chord-a1 arc thread segments of said internal thread are not impaired when the insert is removed or driven into the bore in thework piece. This is attributable to the fact that the driving torque is imposed upon chordal arc segments strong enough to susin said bore in said workpiece, said body having a bore incorporating an internal thread, and having a thin wall.

between said internal and external threads, all of said internal threads being load-carrying threads engageable by a threaded member entering through the upper extremity of said body, said internal threads being constituted by a pluralityof successive convolution-s having 7 disposed radially outwardly of said drive grooves, Whereby the structural integrity of the major diameter portions of the. successive convolutions of the internal threads is maintained, saiddrive grooves occupying a minor'por- 7 tion ofthe circumferential length of any given convolution of said internal threads, thereby formingchordal arc segments in said successive convolutions, the terminal portions of saidisegments being triangular and being formed by the 'side walls of said drive grooves, said drive grooves providing means through which high torque can be applied in driving said insert without causing any substantial reduction in the strength of said internal threads to resist axial stripping when a threaded member;

is tightened therein.

2. An insert as defined in claim 1, wherein the depth of the drive groovesis about to90% of the radial dimension of said internal threads.

3. An insert as defined in claim 1, wherein the drive grooves are V-shaped and the sides thereof are disposed on an angle of about 120, and wherein'the bottom of the drive grooves is rounded. I V

4. An insert 'asdefined in claim 1, wherein the depth of the drive grooves is about 25% to 90% of the radial dimension of said internal threads, and wherein the drive grooves are V-shaped and the sides thereof are disposed 'ternal thread is a self-tapping thread, and wherein the tain the applied torque. Thus, freque'nt removal and/or lower extremity of the body is provided with slots that decrease in depthin a direction toward the upper extremity of said body. 1 a

References Cited by the Examiner UNTTED STATES PATENTS 2,083,092 6/37 Richer -45 2,375,249 5/45 Richer 85-45 2,400,318 5/46 Rosan 8547 2,455,885 12/48 Theurer 8547 V FOREIGN PATENTS T 173,307 2/35 Switzerland.

' 247,514 12/47 Switzerland.

EDWARD C. ALLEN, Primary Examiner.

CARL W. TOMLIN, Examiner. 

1. AN INSERT ADAPTED TO BE INSTALLED IN A WORKPIECE HAVING A BORE, COMPRISING: AN ELONGATED CYLINDRICAL BODY HAVING AN EXTERNAL THREAD FOR MOUNTING SAID INSERT WITHIN SAID BORE IN SAID WORKPIECE, SAID BODY HAVING A BORE INCORPORATING AN INTERNAL THREAD, AND HAVING A THIN WALL BETWEEN SAID INTERNAL AND EXTERNAL THREADS, ALL OF SAID INTERNAL THREADS BEING LOAD-CARRYING THREADS ENGAGEABLE BY A THREADED MEMBER ENTERING THROUGH THE UPPER EXTREMITY OF SAID BODY, SAID INTERNAL THREADS BEING CONSTITUTED BY A PLURALITY OF SUCCESSIVE CONVOLUTIONS HAVING MAJOR AND MINOR DIAMETERS, AND A PLURALITY OF LONGITUDINAL DRIVE GROOVES EXTENDING ACROSS ALL OF SAID INTERNAL THREADS AND BEING ENGAGEABLE BY A DRIVING TOOL THROUGH SAID UPPER EXTREMITY OF SAID BODY FOR DRIVING SAID BODY INTO SAID WORKPIECE, SAID DRIVE GROOVES HAVING THEIR BASES LOCATED INWARDLY OF SAID MAJOR DIAMETER AND OUTWARDLY OF SAID MINOR DIAMETER OF SAID INTERNAL THREADS, WHEREBY SAID DRIVE GROOVES DO NOT EXTEND INTO AND WEAKEN THE WALL BETWEEN SAID INTERNAL AND EXTERNAL THREADS, THE LIMITED DEPTH OF SAID DRIVE GROOVES LEAVING UNIMPAIRED CIRCUMFERENTIALLY CONTINUOUS MAJOR DIAMETER THREAD PORTIONS DISPOSED RADIALLY OUTWARDLY OF SAID DRIVE GROOVES, WHEREBY THE STRUCTURAL INTEGRITY OF THE MAJOR DIAMETER PORTIONS OF THE SUCCESSIVE CONVOLUTIONS OF THE INTERNAL THREADS IS MAINTAINED, SAID DRIVE GROOVES OCCUPYING A MINOR PORTION OF THE CIRCUMFERENTIAL LENGTH OF ANY GIVEN CONVOLUTION OF SAID INTERNAL THREADS, THEREBY FORMING CHORDAL ARC SEGMENTS IN SAID SUCCESSIVE CONVOLUTIONS, THE TERMINAL PORTIONS OF SAID SEGMENTS BEING TRIANGULAR AND BEING FORMED BY THE SIDE WALLS OF SAID DRIVE GROOVES, SAID DRIVE GROOVES PROVIDING MEANS THROUGH WHICH HIGH TORQUE CAN BE APPLIED IN DRIVING SAID INSERT WITHOUT CAUSING ANY SUBSTANTIAL REDUCTION IN THE STRENGTH OF SAID INTERNAL THREADS TO RESIST AXIAL STRIPPING WHEN A THREADED MEMBER IS TIGHTENED THEREIN. 